Ultrafast Imaging with Slow Camera

Phys.org: At the 2019 American Physical Society Meeting on Marc 4, 2019 in Boston, John Kolinski of EPFL in Lausanne, Switzerland, will present a new imaging technique known as the virtual frame technique that he and colleagues Samuel Dillavou and Shmuel Rubinstein of Harvard University developed that enables ordinary digital cameras to capture millions of frames per second for several seconds while maintaining high spatial resolution. He will also participate in a press conference describing the work. Information for logging on to watch and ask questions remotely is included at the end of this news release.

The virtual frame technique uses a camera sensor's bit depth, the amount of information the sensor can obtain, to dramatically increase frame rate. Cracking and many other physical processes are binary; for example, material is either cracked or not cracked. Thus, only two bits are needed to image a crack. An image sensor with a bit depth of 16 bits has more than 65,000 color or grayscale values, meaning it is possible to produce thousands of virtual frames during a single exposure. Using precise camera timing and a short pulse of intense light can increase frame rates even further. "In a recent study using the virtual frame technique, we obtain virtual frame rates exceeding 60 million per second using precise time-gating and a camera sensor with substantial bit-depth," Kolinski said.

Using the virtual frame technique, virtually any camera can directly image dynamic cracks as they form. Additionally, it can be used to study other fast physical processes that happen at interfaces between solids and fluids such as wetting that occurs when a liquid drop hits a material surface. The only requirement is that the solid be opaque, whether it's a construction material or soft substance such as a polymer. "Essentially any material could be imaged with the virtual frame technique," Kolinski said.

Archiv.org paper "Virtual Frame Technique: Ultrafast Imaging with Any Camera" by Sam Dillavou, Shmuel M Rubinstein, John M Kolinski reveals more details: